Manganese: Inorganic & Coordination ChemistryBased in part on the article Manganese: Inorganic & Coordination Chemistry by Charles A. McAuliffe, Stephen M. Godfrey, & Michael Watkinson which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.

Abstract

This article covers the last 10 years of the inorganic and coordination chemistry of manganese at oxidation states (II), (III), (IV), (V), (VI), and (VII), as well as multinuclear compounds having oxidation states (II)–(IV) with both unitary and mixed valencies. The common ligands for manganese compounds involve the donor atoms nitrogen, oxygen, and the halogens while only few are known with other group V and group VI donors. One of the major areas of expansion has been the multinuclear complexes that are relevant to such diverse fields as metalloenzymes and single‐molecule magnets. Besides the small clusters, comprising two to four metal ions synthesized to model the structures and functions of manganese metalloenzymes, a lot of interest has been invested in larger clusters, not only for their biological relevance, but also for the development of materials with novel magnetic properties. Significant advances have been also been made in the chemistry of higher oxidation state manganese complexes (V), (VI), and (VII).

C–C Bond Fluorination via Manganese Catalysis

“…To our surprise, subjecting methyl ether 1a′ to our conditions resulted in significant formation of fluoroketone product 2a (35%), although this amount is reduced compared to alcohol substrate 1a (82%) under otherwise-identical conditions (Figure c). While these results show that alkoxide formation is not required for our fluorination reaction, these results are consistent with the ability of manganese to form complexes with both alkoxide and ether ligands, potentially allowing for an inner-sphere oxidation of the substrate by high-valent manganese in either case . The reduced efficiency of ether substrate 1a′ , when compared with alcohol 1a , might then arise from factors such as increased steric encumbrance disfavoring coordination or the rate of demethylative C–O cleavage being slower than deprotonation.…”

Questing for homoleptic mononuclear manganese complexes with monodentate O-donor ligands

“…Due to the stabilization of the half-lled d shell and the low charge of the metal center, typically Mn(II) complexes exhibit a HS conguration (S = 5/2), 42 Mn(II) centers in low spin (LS) congurations being very scarce. 14,23 Additionally, because of the weak/medium-eld character of the teate ligand, a HS is expected for 1 all the more. 29 In line with this, 1 was determined to have an effective magnetic moment of m eff = 5.87 m B (Fig.…”

“…[19][20][21][22] Notably, the chemistry of manganese complexes with oxygen ligands is mainly dominated by polymetallic species, including oxo ligands in the higher oxidation states, whereas alkoxides or carboxylates are the preferred ligands for lower oxidation states. 14,23,24 To prevent aggregation and enable the formation of mononuclear complexes, bulky alkoxide ligands, as well as uorinated ones, constitute suitable ligand scaffolds. 25,26 In this regard, the pen-tauoroorthotellurate group (teate, OTeF 5 ) also offers unique possibilities, as it provides an O-donor ligand system with a low tendency to bridge metal centers.…”

“…These structures are unusual, as most of the known manganese(II) complexes with O-donors are heteroleptic, ranging from mono-and dinuclear coordination compounds to clusters of different sizes, or even polymeric chain structures. 14,23,24 In this regard, also Mn(II) complexes containing two alkoxido or aryloxido ligands and additional solvent molecules are known. [38][39][40] In our case, the use of a non-donor solvent has further helped isolate the homoleptic species, which in conjunction with the low tendency of the teate to bridge metal centers gives rise to the monomeric nature of the compound.…”